title: Association between second-trimester cervical length and primary cesarean delivery.
abstract: OBJECTIVE
  To evaluate whether an increased ultrasonographic cervical length in the second trimester is associated with an increased frequency of cesarean delivery.
  
  
  METHODS
  This is a retrospective cohort study of nulliparous women with a singleton pregnancy who underwent routine cervical length screening between 16 and 24 weeks of gestation and labored after 34 weeks of gestation at a single tertiary care hospital. Women were grouped by cervical length quartile, and the association between cervical length quartile and cesarean delivery was determined in both univariable and multivariable analyses.
  
  
  RESULTS
  For every additional centimeter of cervical length, the odds of cesarean delivery increased by 20.3%. Similarly, the frequency of cesarean delivery increased with increasing second-trimester cervical length quartiles (17.4%, 22.3%, 21.8%, 27.7%; P<.001). This association persisted in multivariable analyses that included gestational age at delivery and induction of labor. This increased risk of cesarean delivery was primarily the result of women with arrest disorders in the first stage of labor (P<.001).
  
  
  CONCLUSIONS
  Increased second-trimester cervical length quartile is associated with an increased frequency of primary cesarean delivery in nulliparous women.
  
  
  METHODS
  : II.
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Northwestern University Feinberg School of Medicine, Chicago, Illinois.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Miller
authors.forename: Allie
authors.initials: A
authors.lastname: Sakowicz
authors.forename: William A
authors.initials: WA
authors.lastname: Grobman
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement; D002585:Cesarean Section / Q000706:statistics & numerical data*; D004420:Dystocia / Q000453:epidemiology / Q000601:surgery; D005260:Female; D006801:Humans; D010298:Parity; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology